so rrofcssor Hugi's Observations on the 



which corresponded to this one. Moreover, it cannot be doubt- 

 ed that the lower crevices are rarer than the others ; and they 

 are seldom found but in glaciers of the first kind, of some ex- 

 tent. I have seen a great number in my last journey on the 

 Fiusteraarhorn. 



" The upper fissures, that is to say, those formed by day, 

 are always the widest at the surface, and terminate towards 

 the bottom in an angular or wedge form. This form is equally 

 observed in the case where the fissure reaches to the rock or 

 fo the soil, at least when an inferior fissure does not meet with a 

 superior one. Among the elevated glaciers of the first kind, no 

 upper or surface fissure can take place, because this mass is 

 still imperfectly aggregated, and contains much air, so that the 

 changes of temperature easily effect the separation of the grains 

 from one another. Moreover, in years abounding in snow, no 

 fissures are observed. It is only when the mass of these glaciers 

 is deep, or when some time has elapsed without their having 

 been again covered with new strata, that the fissures which are 

 formed at the bottom during the night or winter, penetrate even 

 to the superior surface. But to speak properly, the fissure itself 

 does not penetrate higher than the third or fourth annual stratum 

 of snow ; and it is only when widened that the frozen ice which 

 again covers it crumbles and falls into the opening, or is reduced 

 to dust by the current of air which escapes from it. It is generally 

 acknowledged, that in the elevated glaciers of the first kind, all 

 the fissures widen towards the bottom, and contract towards 

 the top ; and also, that these fissures are much more dangerous 

 than tliose of the lower glaciers which contract towards the 

 bottom, because the inferior crevices of these glaciers do not 

 close in winter. In agreement with these facts, it is, as we have 

 already seen, that in a glacier of the first kind, its mass, on ap- 

 proaching the soil, where it is continually melting by means 

 of the heat of the earth, develops itself, arranges itself and 

 becomes more and more like in its texture to a glacier of the 

 second kind." 



We are entitled, from what precedes, to conclude, that the suc- 

 cession of the temperatures of day and night, summer and win- 

 ter, constitutes the upper and under surfaces of the glaciers into 

 opposite states. The reheating produced duringgumnier, and 



